Method for producing nonwoven webs from unordered fibres

ABSTRACT

A method for producing uniform nonwoven webs from a supply of unordered fibre material includes discharging a quantity of fibre material onto a needle-type transport system having needles which are movable along a transport path, taking-up the fibre material by way of the needles on the needle-type transport system, transporting the fibre material in the needle-type transport system to an end of the transport system, discharging the fibre material onto an opening roller, separating the discharged fibre material on the opening roller and transferring the fibre material which has been separated on the opening roller onto a cylinder. An apparatus for producing uniform nonwoven webs includes a needle-type transport system for transporting fibre material along a transport path, an opening roller positioned along the transport path adjacent one end of the transport system and a rotatable cylinder positioned adjacent the opening roller for receiving the fibre material from the opening roller.

FIELD OF THE INVENTION

The invention relates to a method for producing uniform nonwoven websfrom unordered fibre material, and to an apparatus for carrying out sucha method.

BACKGROUND OF THE INVENTION

There are numerous methods and appliances for the qualitative andquantitative testing of textile fibres. In many test methods, theunordered fibre material, for example cotton in flock form, cannot bemeasured immediately, but must first be processed into nonwoven webshaving a parallelized fibre position. These webs are then used as testsamples for obtaining measured quality values on the fibre material and,in the form of continuous nonwoven webs, as a preliminary step in themanufacture of threads or yarns from the fibre material.

Known appliances for the opening of fibre flocks consist conventionallyof a pair of feed rollers and of an opening drum. A subsequent cylinderreceives the opened material, and then stores it or transports itfurther. The pair of feed rollers ensures controlled material guidancewhich is imperative in view of the high degree of opening necessary inthe fibre flocks. In such opening appliances for fibre flocks, there isa need to produce the desired sliver, if possible, without the fibrebeing damaged. Appliances of this type according to the state of theart, for example cards, have a high throughput, but, at the same time,the fibres are nevertheless damaged to a considerable extent. In cardsaccording to the state of the art, it is also already known to structurethe feed rollers, for example by the formation of spirals on the surfaceof the feed rollers or on a clothing having elements arranged in thedirection of run and resembling small hooks. These structures haveprimarily the function of preventing the fibres from adhering to therollers. A selective retention of the fibres is not possible with thesestructures, thus leading to increased fibre damage in the fibre samplesobtained thereby.

During the feed Of unordered fibre material by means of a pair of feedrollers to an opening roller provided with a "card clothing", the fibrematerial is opened and a uniform nonwoven is obtained from it. Duringthis, the pair of feed rollers moves preferably at a lowercircumferential speed than the opening roller. At least one feed rollercan likewise be provided with a "card clothing", the elements of this"clothing" extending counter to the direction of rotation of the feedroller. The pair of feed rollers retains the still unordered fibrematerial selectively along a line, while the "card clothing" of theopening roller continuously seizes some of the fibres and opens them. Anonwoven is then obtained from these on the subsequent folding roller.

In textile technology, the "card clothing" of a roller is meant todescribe phrase the attachment of a series of narrow bands on the outersurface of the roller, which are equipped with small teeth or smallhooks usually inclined either in the direction of rotation or counter tothis. Likewise, a corresponding design of the outer surface of theroller itself, which can be obtained, for example, by engraving orrolling and by means of which small teeth or small hooks are attached tothe outer surface of the roller, can also be designated as a clothing.For the sake of brevity, such small teeth and small hooks will becombined hereafter under the term "small hooks".

In the method mentioned, the individual fibres of the unordered fibrematerial are retained only along a line. Now if the opening roller drawson a longer fibre, then the remaining fibres behind the retaining lineare drawn towards the feed rollers. There is consequently always anexcess of fibre material between the feed rollers, thereby increasinglyreducing the selective effect of the clothing on one of the two feedrollers. Finally, the fibre material is clamped again. Now if a fibre isseized by the opening roller, then the retaining force is so high thatthe fibre is torn off. The resulting nonwoven web therefore no longerfully possesses the quality features of the unordered fibre material andconsequently can no longer be considered as a completely representativetest sample. However, the torn-off pieces of the long fibres also have aquality-reducing effect on the yarn when the nonwoven web is used as apreliminary stage in yarn production.

Furthermore, EP-B1-0,247,420 discloses an appliance for ordering theends of fibres for fibre-length measurement, in which a nonwoven isintroduced into a needle-type transport device consisting of a pluralityof needle combs and is transported intermittently by this to a gripperdevice, by means of which a sample can be extracted from the nonwoven.The needle-type transport device in this known appliance consists of a"needle bed". This term is meant to describe a series of parallel combswhich are equipped with needles and which can be moved transverselyrelative to the comb direction. While the nonwoven is at rest, the combof the needle bed which is the foremost in the transport destinationdirection is moved into the last position of a lower comb series havingan opposite direction of transport. The comb located in the foremostposition and belonging to this lower comb series is simultaneously movedback into the needle bed as the rearmost comb. During transport, theneedle bed has no appreciable influence on the orientation of the fibresin the nonwoven. The needle bed serves merely to retain the nonwovenwhile a part sample is being obtained in order to determine thefibre-length distribution.

Further needle-type transport systems, already on the market, of N.Schlumberger & Cie. NSC are known, for example under the designation"Intersectingstrecke GN 6" ["Intersecting drafting frame GN 6"] (Companyprospectus Intersectingstrecke GN6, pages 8/9, and Company prospectusGN6, page 5) or "Kettenstrecke GC13"["Chain drafing frame GC13"](Company prospectus, page 5), in which, instead of a gripper (as inEP-B1-0,247,420), a pair of rollers is mounted, and by means of thisslivers or nonwovens can be combed, unfelted and folded. However, theseknown needle-type transport systems or needle-type drafting frames arenot suitable for the opening of unordered fibre material.

The object on which the invention is based is to provide a method bywhich a uniform nonwoven web can be produced from unordered and unopenedfibre material better than in the disclosed methods, along with thegreatest possible preservation of the fibre quality, especially thefibre-length distribution.

Further advantageous embodiments of the invention are described below.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

Two exemplary embodiments of the invention, which at the same timeexplain the operating principle, are illustrated in the drawings and aredescribed in more detail below, in which:

FIG. 1 shows a diagrammatic representation of an apparatus for carryingout the method according to the invention;

FIG. 2 shows a diagrammatic representation of a modified apparatus forcarrying out the method according to the invention;

FIG. 3 shows a partial section through a needle-type drafting frameaccording to the state of the art; and

FIG. 4 shows a partial section, similar to that of FIG. 3, through anapparatus according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

The apparatus 1 illustrated in FIG. 1 consists of an open supplycontainer 2, in which unordered fibre material 3 is located, a pair offeed rollers 4, 5 with a first feed roller 4 and a second feed roller 5,and a needle bed 6 with an upper comb series 11 and a lower comb series12. The needle bed 6 consists of individual combs 7,i which are equippedwith needles that engage into a still unopened nonwoven web 10 to bemanufactured by the apparatus and which move from the pair of feedrollers 4,5 in the direction of the opening roller 8 by means of atransport device (not shown). Further details of the needle bed 6,especially relating to its transport device, are described inEP-B1-0,247,420 and, moreover, are known from the abovementionedappliances on the market, for example of N. Schlumberger & Cie.

The opening roller 8 is followed by a cylinder 9, preferably in the formof a folding roller, on which the opened fibres are folded, thus finallyresulting in the opened nonwoven web 10.

Since the circumferential speed of the opening roller 8 is much higherthan the transport speed of the needle bed 6, the fibres seized by theopening roller 8 are immediately drawn out of the nonwoven and aretransported as individual fibres onto the cylinder 9, with the resultthat a uniform opened nonwoven web 10 is obtained. The fibre tufts ofdiffering density are thus opened by means of this drawing-outoperation.

The unordered and unopened fibre material 3 located in the supplycontainer 2 is continuously seized and discharged by the pair of feedrollers 4,5 in quantities which are small in comparison with thissupply. At the same time, the nonwoven web 10 is preformed between thefeed rollers 4,5, runs by means of the combs 7,i of the needle bed 6 tothe opening roller 8 and further to the cylinder 9 (preferably in theform of a folding roller), with the conversion of the unordered fibrematerial 3 into a nonwoven web 10 consisting of opened fibres beingperfected with each transfer.

The needle bed 6 runs slightly faster than the circumferential speed ofthe feed rollers 4,5, so that no lap can occur between the feed rollers4,5. The pair of feed rollers 4,5 discharges the quantities of fibrematerial 3 to be drawn off onto the needle bed 6 which consists of combs7,i movable individually in the direction of the nonwoven web 10 andequipped with needles. The needles of the combs 7,i take up the fibrematerial 3. As a result of this operation, the fibre material 3 isconverted into a nonwoven web 10. In the textile industry, the term"opening" is meant to describe the increase in the state of order of afibre structure, highly entangled fibres being drawn apart from oneanother or "separated". This opening takes place during the transfer ofthe nonwoven web 10 onto the opening roller 8.

The transport device (not shown) of the needle bed 6 additionally causesthe following movements: the particular comb 7,n closest to the feedrollers 4,5 in the upper comb series 11 is transferred, in the course ofthe transport movement, into the comb position 7,l closest to the feedrollers 4,5 in the needle bed 6. At the same time, the comb 7,n/2closest to the opening roller 8 in the needle bed 6 is transferred intothe comb position 7,n/2+1 closest to the opening roller 8 in the uppercomb series 11. Thus, the combs 7,i are continuously exchangedcyclically and are moved along the needle bed 6 by means of thetransport device. The movement of the transport device can take placecontinuously or intermittently. The needle bed 6 must expediently belonger than the largest fibre length which occurs.

Located on the side of the needle bed 6 on which the nonwoven web 10runs is a pressing-in device 12 which moves towards the needle bed 6 andback again, at the same time passing through between the combs 7,i andrepeatedly pushing the nonwoven web 10 back into the needle bed 6. As aresult, in contrast to the "needle-type drafting frames" according tothe state of the art, the work can be carried out with a one-sidedneedle bed.

As shown in FIG. 2, the needle bed 6 can also take the form of a pair ofneedle bands 16. The two needle bands 16 equipped with needles 17 run ontwo respective pairs of drive cylinders 22. The drive cylinders 22 canbe driven electromotively (not shown in the drawing) and can becontrolled together with the remaining elements of the apparatus 1. Thetwo needle bands 16 are arranged parallel to one another in such a waythat their needles 17 can engage in one another and thereby take up thefibre material 3. For this purpose, the respective pairs of drivecylinders 22 of the two needle bands 16 are to be moved in opposition,so that the parts of the two needle bands 16 bearing on one another movetowards the opening roller 8 in the same direction.

The remaining elements of this modified apparatus are already describedin connection with FIG. 1. The advantage of this modified version is amechanism which involves little outlay and which is therefore cheaper.

In the two embodiments according to FIG. 1 or 2, a limiter 13 isexpediently installed between the opening roller 8 and the needle-typetransport device 6;16 and prevents the fibres from being liftedvertically out of the needles 7;17 by the opening roller 8, thusresulting in a reduction in the retaining force and impaired opening.

A holding-down device 14 is expediently mounted on a lever 15 betweenthe opening roller 8 and the cylinder 9 (preferably in the form of afolding roller). In the case of a multi-layer application of thenonwoven web on the cylinder 9, this holding-down device 14 ensures thatthe fibre fractions or fractions of nonwoven web previously applied tothe latter are held down, for example before a new fraction of nonwovenweb is added.

At least one of the feed rollers 4,5 can possess knobs, that is to saynipple-like elevations on its outer surfaces, or a clothing having smallhooks counter to their running direction, in order to bring about abetter fibre draw-in.

The opening roller 8 is expediently equipped with a clothing, the smallhooks of which lie in the direction of run of the opening roller 8. Thecylinder 9, preferably taking the form of a folding roller, should alsobe equipped with a clothing having small hooks in the direction of run,so that the opened fibres on the opening roller 8 can be received. Thecircumferential speed of the cylinder 9 must be higher than that of theopening roller 8.

The variations in fibre-length distribution are minimal in the methodaccording to the invention. The opening according to the invention ofthe fibres takes place between the needle-type transport device 6;16 andthe opening roller 8. The needle-type transport device 6;16 generatesthe retaining force and the opening roller 8 the drawing-out force.These two forces must be coordinated with one another in the bestpossible way; if the two forces are too high, the fibre is torn apart;if the two forces are too low, the opening which can be achieved ispoor. The advantage of the method according to the invention is that theretaining force is selective and over a large area. Selective means, inthis respect, that each fibre is retained individually according to itslength by a few needles. In the conventional clamping method accordingto the state of the art, the fibres are clamped along a line, thusresulting in an excessively high retaining force and therefore in fibredamage. As regards retention along a line, the fibres are increasinglycompacted behind the retaining line, thus leading to an increase in theretaining force and to damage to the fibres.

FIGS. 3 and 4 illustrate the problem of small hooks of fibre. As shownin FIG. 3, in the methods according to the state of the art, thesituation can arise that the needle tip 21 of the needle comb 7 issurrounded by a fibre 20 forming a closed loop. If, as in the state ofthe art, the drawing-off device consists of a pair of rollers 18,19which clamps the fibres along a line and which thus draws them out ofthe fibre material, then the fibre 20 is necessarily destroyed.

As shown in FIG. 4, in the method according to the invention thisproblem is solved by the use of an opening roller 8 having clothings.The fibre 20 forming a small hook is received by the opening roller 8only when the retaining needle is removed. The drawing-off forces aretherefore likewise selective, in contrast to the clamping line in the"needle-type drafting frame" according to the state .of the art (FIG.3). In the method according to the invention, therefore, thefibre-length distribution is better preserved than in the methodsdisclosed hitherto.

The method according to the invention thus achieves the object ofproducing a uniform nonwoven web 10 from unordered fibre material 3better than the disclosed methods, along with the greatest possiblepreservation of the fibre quality, especially the fibre-lengthdistribution.

We claim:
 1. Method for producing uniform nonwoven webs from a supply ofunordered fibre material comprising:A) discharging a quantity of fibrematerial onto a needle-type transport system having needles which aremovable along a transport path in a material flow direction; B)taking-up the fibre material by way of the needles; C) transporting thefibre material on the needle-type transport system to an end of thetransport system and then discharging the fibre material onto an openingroller; D) separating the discharged fibre material on the openingroller; and E) transferring the discharged fibre material which has beenseparated on the opening roller onto a cylinder in the form of anonwoven web.
 2. Method according to claim 1, wherein the fibre materialis discharged onto the transport system by way of a pair of feedrollers.
 3. Method according to claim 1, wherein the needle-typetransport system is a needle bed comprised of combs which are movableindividually in the direction of the nonwoven web to be formed and whichare equipped with the needles.
 4. Method according to claim 3, includinga transport device which moves the combs of the needle bed in series inthe direction of the transport path.
 5. Method according to claim 4,wherein the transport device transfers the comb of the needle bed whichis closest to the opening roller into a comb position closest to theopening roller in an upper comb series, and also transfers the comb ofthe upper comb series which is closest to the feed rollers into a combposition closest to the feed rollers in the needle bed to thereby effecta continuous cyclic exchange of the combs in which the combs in theneedle bed move from the feed rollers to the opening roller and thecombs in the upper comb series move from the opening roller to the feedrollers.
 6. Method according to claim 4, wherein the fibre material istransported continuously.
 7. Method according to claim 4, wherein thefibre material is transported intermittently.
 8. Method according toclaim 3, including retaining the nonwoven web in the needle bed by apressing-in device which passes between the combs.
 9. Method accordingto claim 8, wherein the combs of the needle bed are moved by a transportdevice, the pressing-in device being moved by the transport device. 10.Method according to claim 1, wherein the needle-type transport systemcomprises two needle bands which are arranged parallel to one another,and including moving the two needle bands by means of drive cylinders,the needle bands being equipped with needles which can engage in oneanother along parts of the two needle bands which face one another inorder to move the fibre material.
 11. Method according to claim 2,wherein the circumferential speed of the feed rollers is lower than thespeed of the needles of the needle-type transport system.
 12. Methodaccording to claim 3, wherein the speed of the needles of theneedle-type transport system is lower than the circumferential speed ofthe opening roller.
 13. Apparatus for producing uniform non-woven websfrom a supply of unordered fiber material comprising a needle-typetransport system for transporting fibre material along a transport path,an opening roller positioned along the transport path adjacent one endof the transport system, and a cylinder positioned adjacent the openingroller for receiving the fibre material from the opening roller. 14.Apparatus according to claim 13, including two feed rollers positionedat an end of the transport system opposite the opening roller. 15.Apparatus according to claim 13, wherein the needle-type transportsystem comprises a needle bed with combs, a pressing-in device (12) andan upper comb series (11).
 16. Apparatus according to claim 13, whereinthe needle-type transport system comprises two needle bands which arearranged parallel to one another, the needle bands being movable bymeans of drive cylinders and being equipped with needles which engage inone another along parts of the two needle bands which face one another.17. Apparatus according to claim 14, wherein at least one of the feedrollers has a clothing with small hooks positioned counter to thedirection of rotation of the feed roller.
 18. Apparatus according toclaim 13, wherein an outer surface of at least one feed roller hasknobs.
 19. Apparatus according to claim 13, wherein the outer surface ofthe opening roller has a clothing with small hooks arranged in thedirection of rotation of the opening roller.
 20. Apparatus according toclaim 13, wherein the cylinder is a folding roller, an outer surface ofthe folding roller having a clothing with small hooks arranged in thedirection of rotation of the cylinder.
 21. Apparatus according to claim13, including a holding-down device mounted on a lever between thefolding roller and the opening roller.
 22. Apparatus according to claim13, wherein the length of the needle bed is longer than the greatestlength of fibre.
 23. Apparatus according to claim 13, including alimiter for retaining the fibres within the needle-type transportsystem, said limiter being positioned between the opening roller and theneedle-type transport system.
 24. Apparatus for providing a uniformopened nonwoven web from a supply of unordered fibre materialcomprising:a feed device for feeding unordered fibre material; a movableneedle bed positioned adjacent the feed device for receiving unorderedfibre material from the feed device and for transporting the fibrematerial as a nonwoven web in a transport direction, said needle bedincluding a plurality of needles which engage and transport the fibrematerial during movement of the needle bed; a rotatable opening rollerpositioned adjacent an end of the needle bed for drawing out fibres fromthe nonwoven web of fibres transported by the needle bed and forcarrying the drawn-out fibres to produce a uniform opened nonwoven webof fibres; and a rotatable cylinder positioned downstream of therotatable opening roller bed with respect to the transport direction forreceiving the uniform opened nonwoven web of fibres from the openingroller.
 25. Apparatus according to claim 24, wherein the needle bedtransports the fibre material at a transport speed, the circumferentialspeed of the opening roller being greater than the transport speed ofthe needle bed.
 26. Apparatus according to claim 25, wherein the feeddevice includes two feed rollers which rotate at a circumferential speedthat is less than the transport speed of the needle bed.